Impurity removal, the purification process from metallurgical grade silicon (MG-Si) required to obtain solar grade silicon (SoG-Si), is crucial to the preparation of silicon-based solar cells. Some processes for boron removal by metallurgical method were reviewed. Secondary refining techniques, including gas blowing, slag treatment, plasma refining, solvent refining and other refining silicon techniques were summarized. The effects of gas species and slag systems on boron removal efficiency were emphatically discussed. Experimental and theoretical investigations show that a united technique of combining water vapor and oxygen gases blowing with slag treatment containing chloride or fluoride has achieved an amazing improvement for boron removal from molten silicon. Plasma refining and solvent refining also display high efficiency but acid leaching treatments, vacuum volatilization, electron beam and directional solidifications are hardly effective to boron removal. As for the potential industrial application of this united technique, the authors propose that some experimental and theoretical studies in dynamics should be further explored.

杂质去除是获得太阳能级硅（SoG-Si）所需的从冶金级硅（MG-Si）提纯的工艺，对于硅基太阳能电池的制备至关重要。综述了冶金法除硼的一些方法。总结了二次精炼技术，包括吹气，炉渣处理，等离子体精炼，溶剂精炼和其他精炼硅技术。着重讨论了气体种类和炉渣系统对除硼效率的影响。实验和理论研究表明，将水蒸气和氧气吹入与含氯化物或氟化物的炉渣处理相结合的联合技术已实现了从熔融硅中去除硼的惊人改进。等离子体精制和溶剂精制也显示出高效率，但是酸浸处理，真空挥发，电子束和定向凝固对去除硼几乎没有效果。至于这种联合技术的潜在工业应用，作者建议应进一步探索动力学方面的一些实验和理论研究。